[Question] Is there any way to create a readonly focusAtom? And is it possible to make it work with atomWithImmer?

For example here’s my atoms:

const pagesAtom = atom([{
  children: ['element 1', 'element 2'],
}]);
const currentPageAtom = atom(0);
const currentPageElementsAtom = atom(get => get(pagesAtom)[get(currentPageAtom)].children);

const { index } = props;
const currentElementAtom = focusAtom(currentPageElementsAtom, optic => optic.nth(index)));

However since first parameter should be a WritableAtom so it doesn’t work. How about implementing something like focusAtomValue and updateFocusAtom to dress this issue?

Also I found that atoms created by atomWithImmer couldn’t be used by focusAtom. I can manually use immer to do the samething in the original atom, but is there a better way to do it?

[dai-shi]

Well, the code for #452 would actually be a few lines.

  (get, set, arg) => {
    if (typeof arg === 'function') {
      set(anAtom, produce(get(anAtom), arg)
    } else {
      set(anAtom, arg)
    }
  }

But, types, tests, and docs wouldn’t be trivial.

[dzcpy]

@dai-shi Well, I solved the readonly issue but not atomWithImmer one. I tried to dig a bit into it to see if I can create a PR, but it turned out that it’s a bit complicated than I thought. Hopefully someone else can work on it to make it more universal.